The invention relates to an apparatus for exerting a spring loaded force on a part such as a workpiece, another component of a machine or other article.
Spring loaded plunger assemblies are used in many manufacturing applications and as components of manufactured products. In manufacturing, they may hold materials in place for tooling and assembly processes, and they perform detent, indexing, positioning and ejection functions as well. In products they perform many similar functions, especially indexing and positioning. In some situations, the amount of force transmitted by the spring to the plunger and must be set precisely for a particular application. That force is determined by the extent to which the spring is compressed when the plunger is not depressed, which is determined by the depth to which a plug (the "force-setting plug") is inserted into the body of the plunger assembly.
Typically, the outside of the body of the plunger assembly is threaded so that the assembly can be screwed into a threaded hole on a machine tool or other device. In some applications, it is necessary or preferable to install and disinstall the assembly by using a screw driver or wrench to apply torque to the force-setting plug, thereby rotating the entire assembly.
Heretofore, a threaded set screw has been used as the force-setting plug. The set screw is screwed into the body of the assembly to the depth needed to produce the desired amount of force to be exerted by the plunger. The set screw may be cemented or otherwise locked into place to attempt to immobilize it against the torque applied in installing and disinstalling the assembly and against vibrations incurred during operations.
It is found in practice that the set screw may loosen, especially when torque is applied to it in order to disinstall the plunger assembly. This may cause significant difficulty and delay in disinstalling the assembly. The set screw may also loosen during installation or during operations. Besides loosening, another disadvantage of using a set screw as the force-setting plug is the cost of threading both it and the rear inner surface of the body of the assembly.